One of the most potent divides in U.S. politics at the moment is the split between urban voters and rural ones. In the special election in Ohio’s 12th Congressional District on Tuesday, for example, there was a 64-point swing in the margin between the Democratic candidate and the Republican from rural Muskingum County to more-urban Franklin County.

That divide overlaps with a lot of other factors, of course. Race, for one: Urban counties tend to be much more diverse. There’s also a divide on economic lines. Less-rural counties (meaning both urban and suburban counties) tend to have higher median incomes, in part because the standard of living in urban areas tends to be higher.

We’re used to charts that look something like this — or, at least, are not surprised by the curve implied by the points below. Less-rural places have higher median incomes than more-rural ones.

But, of course, that pattern isn’t uniform. That box at the far shows a number of counties that are both entirely rural (meaning that the Census Bureau identified its entire population as living in rural areas) and earn incomes above the national median.

What counties are those? As it turns out, it’s an interesting mix.

Consider the outlying counties on the chart above. The county with the highest median household income (in inflation-adjusted 2016 dollars) is Loudoun County, Va. in the D.C. suburbs. The county with the highest income that’s at least half rural is Hunterdon County, N.J., north of Philadelphia. The county with the highest median income that’s entirely rural? Elbert County, Colo.

You’d be forgiven if you’ve never heard of Elbert County. Curious about why it held that position, I spoke with a resident of the county who declined to offer her name. She offered that the most likely explanation for why incomes were so high in Elbert, relatively speaking, is geography. It’s rural, but it’s also a bedroom community for the large cities of Colorado Springs and Denver, each of which is about an hour away. She has a lot of friends and neighbors who make such a commute, she said, though she herself doesn’t.

Median household income is one way to look at wealth. Another is to look at the number of wealthy people. The Census Bureau breaks out information on the density of households at certain income levels, allowing us to determine how many households in each county have incomes of $200,000 or more. That chart looks a bit like the one above, but the counties that stand out are different.

Hunterdon County is back, as is a D.C. suburb (Falls Church). Goochland County, Va., outside Richmond, has one of the highest densities of wealthier households of any heavily rural county. But the county with the highest density of wealthier households is Glasscock County, Tex.

You can probably guess why a county in Texas holds that distinction, but we’ll get back to that in a second.

An interesting bit of data that emerges here is that there are far more counties that are 100 percent rural that have median incomes over the national average than there are counties that have no rural areas that have similarly high incomes. But that’s a function of there being so many rural counties. For the same reason, it’s also the case that there are more rural counties with a density of households with at least $200,000 in income that’s over the national average.

There are not a lot of counties that are 100 percent rural with median household incomes over the national figure and a density of wealthier households that also beats the national percentage.

Here are all of them:

Fourteen of them are in North Dakota and Texas, and most of those counties make the list because of the oil industry. North Dakota is the epicenter of the fracking boom, and residents of the state — particularly on the western border over the Bakken shale formation — have benefited economically. Same goes for those four counties in western Texas (including Glasscock) that sit on top of the Permian basin. The energy boom in recent years has meant economic success in places where the population is entirely rural.

These 24 counties uphold one stereotype, though: All but three voted for President Trump in 2016. On average, the counties on the map above backed Trump by 48 points. (The three exceptions? Alpine County in California, San Juan County in Washington and San Miguel County in Colorado.)

There are also more of those counties than there are counties with no rural population that have above-average median incomes and wealthy households. Only 13 counties with no rural residents exceed the national figures on those metrics.

Those counties voted for Hillary Clinton in 2016 by an average of 46 points.